Floating wind’s head start – don’t be surprised by rapid progress

The world’s largest floating offshore wind farm is Japan’s Fukushima Forward project. Operational since 2013, it now includes three turbines with a total capacity of 14 MW. This accounts for nearly half of the approximately 30 MW global floating wind capacity.

Considering the average European grid-connected fixed offshore wind farm weighs in at 380MW, you’d be forgiven for thinking floating offshore wind is a drop in the ocean.

However, in the UK alone, Statoil is installing the 30 MW Hywind demonstration project this year – itself equal to current global capacity. By the end of 2018, Kincardine pilot and Windfloat development projects could have added 48 MW and 24 MW respectively, taking Europe’s total to 88 MW.

This rapid increase will not be confined to Europe and owes a debt to the huge technical strides already made in the oil and gas (O&G) sector as well as the fixed turbine offshore wind industries. The market opportunity for floating wind is huge and a lot of people might be surprised by the speed of its progress.

Why floating wind?

Offshore wind has been one of the biggest renewable energy success stories. In 2016, in Europe alone, there were 3,589 grid-connected wind turbines, with an average capacity of 4.8 MW.

Europe has led the way, at least partially, because it benefits from large areas of shallow seabed. On average, those turbines are in waters just 29m deep.

The Fukushima Forward website shows what Japanese planner are thinking.

This has made Europe an ideal nursery for the fledgling industry, but once you get to depths greater than 50m, fixed-foundation structures increase in cost and complexity. As a result, advanced economies with deeper coastal waters, such as the US and Japan, have fewer suitable sites for fixed-foundation wind farms. Access to offshore wind energy for such sites will depend heavily on floating structures to support turbines in deeper waters.

Alongside these geographical factors, there are political and economic ones pushing these countries to invest in floating wind too. In the case of Japan, a paucity of domestic energy resources has left the country reliant on fossil fuel imports such as LNG – especially since the 2011 Fukushima disaster forced a rethink on nuclear power. Offshore wind offers a chance to reduce this reliance on foreign imports.

By contrast, the US is endowed with abundant native energy resources, with the shale boom still in full swing. What’s more, it has another source of abundance to the North, being linked to hydrocarbon-rich Canada by pipeline, too. However, there are still economic drivers for offshore wind – more renewable energy means more fossil fuels can be exported rather than used. Differences from state to state will also drive interest – look at California – a green-minded state without energy resources of its own, powering its economy would be one of the largest the world has seen.

Finally, closer to home, there’s the UK. While the UK has been a true leader on fixed offshore wind already, larger offshore wind farms have been predominantly installed in English coastal waters, where the continental shelf is shallow and where there are often favorable grid connection points. In Scotland, we are now seeing larger wind farms such as the 588 MW Beatrice project currently under construction as well as demonstrations projects such as the European Offshore Wind Development Centre, one of the first deployments of innovative 66 kV array and export cabling. As the Scottish government sets its own ambitious plans for renewable energy, floating offshore wind will be of major interest.

Floating’s advantage

As a young technology, floating offshore wind is significantly more expensive than its older sibling, fixed turbine wind. That may well remain the case for a time to come – it’s no mean feat of engineering to design and manufacturer floating bases that can support the world’s tallest turbines.

However, floating wind does enjoy some theoretical advantages. First off, it should be possible to use bigger, more powerful turbines, requiring fewer turbines per MWH of power produced, thereby reducing costs.

Being further from the coast, floating farms are more able to exploit the potentially stronger wind resources away from coastal areas.

Perhaps most importantly though, floating turbines can be almost completely manufactured and installed onshore before being towed into place. Floating turbines are also moveable which means critical maintenance and repair activities could be performed after towing the floating turbine back to shore, enabling the use of heavy-lift dockside equipment rather than more costly heavy lift specialist vessels. Compare this to fixed technologies, which require difficult construction or maintenance work on site, in challenging subsea environments and subject to weather windows. Not only is this work easier, it also reduces the need for chartering expensive, specialised vessels during wind farm construction.

A handy head start

Far more goes into a floating offshore wind farm than the turbine design itself. First, you need the technology to make it float, then you need to tether the floating structure to the seabed – both elements of which must withstand extreme offshore environments. Then you need high-performance cabling – both for intra-array power collection or distribution as well as export cabling for transmission back to shore.

Fortunately, these are industries that many global engineering firms have already spent decades perfecting in the O&G and fixed turbine spaces.

For example, the fixed turbine space has invested millions in designing and manufacturing ever more advanced and cost-effective turbines, as well as developing processes and technologies around offshore inspection and maintenance that contribute significantly to the ongoing cost of a wind farm.

However, floating wind also owes a debt to floating O&G projects in deep and ultra-deep waters.

For example, floating production, storage and operation platforms in O&G have already largely solved issues around stable flotation and seabed tethering, and have applied that expertise in countless real-world applications.

Similarly, cable manufacturers have developed innovative 66kV ‘wet design’ cables, which offer weight and endurance benefits. Conventional cable designs require heavy metallic barrier layers at this voltage, which can have significant reliability or cost implications when used in a dynamic floating cable configuration. 33kV dynamic cables, which can withstand the movement and stress of a non-fixed platform – are already proven in floating O&G applications, and 66kV are not far behind for floating wind with the Windplus consortium’s, WIndfloat Atlantic project leading the way in 2018.

It’s not just the cables themselves that floating wind owes a debt to the O&G sector for – it also benefits from the supplementary tools developed by the industry. For example, Orcina has already developed advanced analytical techniques for offshore engineering, allowing engineers to simulate storm conditions and model the performance of moorings, cables and umbilicals beneath a floating structure. The software simulation allows multiple load cases and scenarios to be analysed, allowing engineers to demonstrate and optimise the subsea system configuration for all potential outcomes. This reduces cost and risk in the detail design phase and the techniques have been developed over hundreds of offshore floating projects.

Obviously, already having these technologies on the market in advance is helpful as time doesn’t need to be spent developing them. However, it also benefits the industry by making offshore wind far more insurable and bankable. After all, if only a few elements of the technology are new, investors and insurers will be far better able to quantify their risk. Aside from the engineering perspective, this makes it smoother for companies to develop the sector from a business perspective.

These technologies are already out there, proving themselves in the field for both O&G and fixed turbine offshore wind. Crucially floating offshore windfarm developers need to draw on the expertise from both the offshore renewables sector and the floating oil and gas sectors, and in doing so the benefits to project success will be significant. From a cable, mooring system and floating structure perspective, floating wind can pose many fundamental new engineering problems to solve, however the vital tools and technical expertise is there in companies who have worked through such complex engineering challenges in floating energy systems around the world. Combine this capability to solve complex engineering challenges with the fact that the demand is clearly there, and you have a compelling reason to think that the floating wind industry could scale at a far faster rate than its fixed-base precursor.

About The Author

Paul Dvorak

Windpower Engineering Editor Paul Dvorak is an experienced mechanical engineer. Paul has seven years of hands on mechanical engineering experience and 23 years of technical writing. Paul is constantly in correspondence with wind turbine manufacturers and wind power researchers. Thanks to this correspondence, he is able to write about wind engineering topics before any other editor in the wind space.

Wind Talk Podcasts

Windpower Editor Michelle Froese interviews the industry's biggest newsmakers and allows them to tell their stories.

Windpower Engineering & Development Digital Edition

Browse the most current issue of Windpower Engineering & Development and back issues in an easy to use high quality format. Clip, share and download with the leading wind power engineering magazine today.